DETRITUS FLOW MANAGEMENT FEATURES FOR DRAG BIT CUTTERS AND BITS SO EQUIPPED

Rock detritus created by a drag bit cutter shearing subterranean formatio n material may flow under the cutter and attach itself to the side surface o f the cutter barrel by differential pressure-induced sticking, and dilate. T his attached material, confined by hydrostatic pressure, can create and stre ngthen a barrier between the cutter and the virgin rock being cut. The detri tus barrier absorbs bit weight and reduces cutter efficiency by impairing co ntact of the cutter with the virgin rock formation. Increasing the friction between the rock detritus and the side surface of the cutter barrel for exam ple by means of grooves or bars (140A) inhibits detritus flow, reduces build up, and allows hydrostatic pressure to contribute to, rather than inhibit, the cutting process. Similar beneficial results may be obtained when hydrost atic pressure drilling fluid is permitted to communicate through holes in th e side surface of the cutter, or through an otherwise permeable side surface alleviating detritus sticking due to differential pressure effects.